U.S. Pat. No. 4,046,889, issued Sept. 6, 1977 describes a group of thioalkanoyl derivatives of azetidine-, pyrrolidine- and piperidinecarboxylic acid derivatives which are useful as inhibitors of the conversion of the decapeptide angiotensin I to angiotensin II, and are therefore useful in reducing or relieving angiotensin related hypertension.
Among the compounds described in the abovementioned patent are those having the structural formula ##STR2## and salts thereof, wherein the variables are as defined hereinafter. These compounds readily convert to the corresponding dimers(through the sulfur atom) and other more polar products in biological fluids such as blood and urine. This conversion presents a problem in running studies to follow the time course of the compounds in the bodies of animals or man.
It is an object of this invention to prevent or minimize the conversion of the compounds illustrated above immediately upon the collection of biological samples containing these compounds, and thus allow for the collection of reliable analytical data.
These and other objectives may be realized by using the method and novel compounds described hereinafter.